Effect of isotope substitution and pressure on the phase transition in triglycine sulphate

• Published in: Physica. B, Condensed matter Condensed matter, 2005-09, Vol.366 (1), p.116-121
• Main Authors: Choudhury, Rajul Ranjan, Chitra, R., Ramanadham, M.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Ferroelectric phase transition; Ferroelectricity and antiferroelectricity; Hydrogen bond; Kdp- and tgs-type crystals; Phase transitions and curie point; Physics
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2005.05.034

A quantitative estimate of dipolar interaction energy causing the order–disorder ferroelectric phase transition in triglycine sulphate (TGS) is obtained and also the effect of small hydrostatic pressures on the dipolar energy is modelled. At high pressures of the order of 2.5 GPa a crystallographic phase transition to a non-ferroelectric phase takes place in these crystals, the spontaneous polarization goes to zero most likely because of the glycine ion GI becoming planar at high pressures. The inverse Ubbelohde effect observed in TGS is successfully explained using the corrected valence bond model. The increase in transition temperature ( T C) on deuteration is associated with the increase in value of the reorientable dipole moment of TGS. A quantitative estimate of increase is obtained using the Mecke dipole function.